Trilobal filamentary yarns



Jan. 12, 1965 G. PITZL TRILOBAL. FILAMENTARY YARNS Filed March 22, 1963 INVENTOR GILBERT PITZL ATTORNEY United States Patent 3,164,949 TRTLOBAL FELAMENTARY YARNS Gilbert Pitzl, @hattanooga, Tenn, assignor to E. 1. du Pont de Nemours and Company, Wilmington, Deb, a corporation of Delaware Filed Mar. 22, 1963, Ser. No. 267,347

6 Claims. (Cl. 57-140) This invention relates to improved synthetic yarns comprising trilobal filaments.

Yarns produced from synthetic polymers in which the filaments are of trigonal cross section have been found to offer substantial improvements with respect to luster, covering power and resistance to soiling if the crosssectional shape conforms to certain parameters as set forth in US. Patents 2,939,201 and 2,939,202, and discussed in greater detail hereinafter.

The said cross-sectional shapes include concavely trilobal sections (as in FIGS. 1 and 2 of Patent 2,939,201) and also triangular cushion shapes as in FIG. 1 of said Patent 2,939,202. All these shapes could be aptly embraced by the term trigonal, in the sense that they are all three cornered shapes. appears to have adopted the term trilobal as a generic term for the various fiber shapes included in the above two patents. Accordingly, this term will be adhered to throughout this specification and claims, and is to be understood in the above indicated generic sense. For the same reason, the expression high-luster, trilobal filaments as used herein shall be understood as referring to filaments of the types described in US. Patents 2,939,- 201 and 2,939,202. These trilobal filaments are characterized by tip radius ratio, modification ratio, and arm angle, all of these parameters being described in detail in the above patents.

It has been found that trilobal filament yarns of this type are generally very attractive when woven into fabrics suitable for womens apparel, such as dresses and blouses. However, certain difficulties have been encountered in producing completely satisfactory fabric for this market. The difiiculty is due to the fact that the high sparkle and luster of the yarn (one of its most desirable features) accentuates streaks and quill junctions caused by small, unavoidable variations in yarn properties arising from slight variations in tension, denier, filament cross section, etc., in the production of the yarn. These variations bring about a marked variation in yarn luster so that different packages of yarn may vary considerably in luster, or relatively abrupt changes in luster may occur within a package. It is almost impossible to control the yarn preparation in a commercial process within sufficiently narrow limits to prevent these highly undesirable non-uniformities.

in the fabric.

Process variations of this magnitude do not cause appreciable non-uniformity in fabric prepared from nonlustrous yarns such as conventional, round cross-section yarn.

It is an object of this invention to provide a high-luster,

However, the practical art trilobal filament yarn of improved uniformity with repect to luster. Another object is to provide packages of trilobal yarn which may be used to produce fabrics that are greatly improved with respect to streaks and quill junctions. Other objects will become apparent from the examples and discussion which follow.

The above objects are accomplished by a yarn comprising a plurality of trilobal synthetic polymer filaments of high luster, the denier of the various filaments differing in a reasonably uniform fashion over an appreciable range, said variation in denier persisting throughout substantially the entire length of yarn in a given yarn package. The magnitude of the range and the distribution of the filaments with respect to denier within this range are characterized (1) by a coefficient of variation (v) not less than 10, (2) a skewness coetficient (a within the range of 7-0.7 to +0.7, and (3) a kurtosis coefficient (a.;) not exceeding 4.0, and preferably between 1.0 and 4.0.

The parameters v, a and a which characterize the distribution of the filaments in the yarn with respect to denier may be calculated, when the deniers of all the fil a ments in the yarn are'known, from the following equations:

s Standard deviation= {M where s The equation will be recognized as the equation of the normal distribution or normal probability curve where P isthe probability or frequency of ocurrence of a deviation of magni-' tude z in a large number of observations. The material within the brackets represents the corrections for skewness and kurtosis. Skewness and kurtosis are measures of the shape of the distribution. Skewness refers to the lack of symmetry and kurtosis measures an excess or deficiency of values in the tails of a distribution. For a symmetrical (normal) distribution the skewness coefiicient (a is 0. Distributions which are unsymmetrical because of an excessive number of high values have a positive skewness, while those which are unsymmetrical because of a preponderance of low values have negative skewness. For a symmetrical or normal distribution the kurtosis coefficient (a )'is 3. When this coeflicient is less than 3 the distribution has shorter tails and squarer shoulders, i.e., has a flatter distribution than the normal distribution and is said to be platykurtic. When the kurtosis coefficient is greater than 3, the distribution has long tails and is more sharply peaked than the normal distribution and is said to be leptokurtic.

Preferably, there will be at least five species of filaments having different deniers in the yarn with no single species constituting more than 35 of the total number of filaments in the yarn. The difference in denier between any two species which are adjacent to each other in the distri- 2,939,202, the spinneret having superimposed thereon a metering plate having a plurality of orifices, each of Ce Patented Jan. 12, 1965 which communicates directly with one of the spinneret orifices as described in the copending application of James S. Cobb, Serial No. 208,748, filed July 10, 1962, issued July 2, 1963, as Patent No. 3,095,607. The extrusion orifices of the spinneret shown in the Cobb application may be replaced by Y-shaped or triangular orifices which provide triiobal-shaped filaments. The orifices of the metering plate should vary in size so that different volumes of polymer are delivered to various of the spinneret orifices to produce filaments within the denier ranges of the present invention when polymer is supplied to the metering plate orifices at a uniform pressure.

- The sole figure in the accompanying drawing represents a photomicrographic view of the cross-section of a typical 34-filament yarn produced according to this invention.

The following examples further illustrate the present invention.

EXAMPLE I Polyhexamethylene adipamide was prepared in the conventional manner. The polymer was melt extruded to form trilobal filaments having a relative viscosity of 40 as described in U.S. Patent 2,939,201 except that a metering plate having round orifices was superimposed on the spinneret, as previously mentioned to vary the denier of the filaments. The filaments were quenched by passing air transversely across them in the conventional manner. The yarn was drawn at a ratio of 2.62 and given a hot relaxation treatment as described in US. Patent 3,003,222, the yarn being permitted to retract 9%.

The number of filaments, the denier. of the filaments, and the diameter in inches of the metering plate holes are shown in Table 1 below. Yarns A, B, C, and D were spun with varying filament deniers as shown in Table 1 below. The coefiicients of variation (v), the standard deviations (s), the skewness coefficients (a and the kurtosis coefiicients (a for these yarns are shown in Table 3. Yarn A bad a modification ratio of 1.62, an arm angle of 45, and a tip radius ratio of 0.43. Yarn B had a modification ratio of 1.60, an arm angle of 47, and a tip radius ratio of 0.44. Yarn C had a modification ratio of 1.53, an arm angle of 51, and a tip radius ratio of 0.42. Yarn D had a modification ratio of 1.55, an arm angle of 52, and a tip radius ratio of 0.45.

For comparison, a control yarn E was spun without the metering plate. The deniers of the individual filaments in the control yarn were determined and the percentage of filaments of each denier were as shown in Table 2 below. The modification ratio for this yarn was 1.50, the arm angle was 55, and the tip radius ratio was 0.44.

The distribution parameters s, a and a for all the yarns are shown in Table 3. The yarns were woven into 104 x 76 taffeta fabric and examined for streakiness. The fabrics were rated in order of their streakiness as reported in table 3 below, a rating of 1 being best, and a rating of 3 being barely satisfactory. All of these fabrics have high luster and sparkle as compared to fabrics from round cross-section yarns.

4 Table 2.--Yarn E (Control) Filaments Denier Number Percent Total 34 Table 3 Fabric Yarn v s a :1 Uniformity EXAMPLE II Polyhexamethylene adipamide was prepared in the conventional manner. The polymer was extruded, as described in Example I, to form trilobal filaments of varying denier and having a relative viscosity of 40. The filaments were quenched and wound into a package in the conventional manner. The yarn was then drawn to a ratio of 4.35 on a draw twister and wound into a package. Trilobal filaments yarn F, having a modification ratio of 1.63, an arm angle of 42, and a tip radius ratio of 0.36, and yarn G having a modification ratio of 1.57, an arm angle of 50, and a tip radius ratio of 0.41, were spun in this manner. The number of filaments of each denier, the denier and the diameter of the metering plate holes in inches are given in Table 4 below.

A control yarn H was spun by extruding the polymer without the metering plate. This yarn had a mean filamerit denier of 6.3. The modification ratio was 1.70, the arm angle is 40, and the tip radius ratio is 0.36. Values for the coetficients v, s, a and (1 are given in Table 5. When yarns F, G, and H were woven into upholstery fabric and the fabric examined for streakiness, fabric from yarn G was found to be of excellent uniformity, while the fabric from yarn F, although acceptable, was somewhat inferior to that from yarn G. The fabric from control yarn H is unacceptable due to excessive streakiness,

Table 1 Yarn A Yarn B Yarn C Yarn D Hole Denier Hole Denier Hole Denier Hole Denier Dla. Dia. Die. Die.

Total 34 Table 4 Yarn F Yarn No. of Filaments 7 Hole Size Denier Hole Size Denier Table 5 Yarn 1) s a; a

21. 4 1. 28 -0. 53 2.08 G 34. 1. 0. l0 1. 51 H (Control) 8. 1 0. 51 0. l0 3. 05

EXAMPLE III Polyhexamethylene adipam-ide was prepared and extruded to form trilobal filaments of varying denier as described for yarn C in Example I. The filaments were quenched in the conventional manner and the yarn was then drawn by passing it around two draw rollers, the second of which had a higher peripheral speed than the first. Between the rollers, the yarnwas passed through an enclosure where steam at 20 .p.s.i.g. and 275 C. was jetted on the yarn. The yarn was drawn to a ratio of 4.0. This yarn, which was designated yarn I, had a modification ratio of 1.50, a tip radius ratio of 0.44, and an arm angle of 55.

For comparison, yarn K was spun Without the metering plate. This yarn has the same average denier, modification ratio, tip radius ratio, and arm angle as yarn J. Also,

for comparison, yarn M, a round cross-section yarn, having variable denier filaments was spun using the metering plate, and yarn L, a round cross-section yarn, was spun without the metering plate.

Yarns J, K, L, and M were woven into 104 x 76 taffeta fabrics and the fabrics were examined for uniformity. The coefficients, v, s, 01 and a and the fabric ratings are given in Table 6 below, a rating of 1 being best and a rating of 3 being barely satisfactory. As indicated in this table, variation of the denier of the round cross-section yarn results in an unsatisfactory fabric while the same procedure applied to the trilobal filament yarn yields a great improvement in fabric uniformity.

The foregoing examples illustrate the value of this invention in preventing quill junctions and streaks in fabrics prepared from high-luster trilobal filaments. The term quill junction refers to that point in a fabric where, during its preparation, the yarn package, i.e., the quill, in the shuttle is exhausted and is replaced by a new package. If the yarns on the old and new packages differ sufficiently in appearance, e.g., in luster, the junction becomes visible, while, if there is no difference in the yarns, the junction is not apparent.

As previously indicated, the term high-luster, trilobal.

filaments as used herein refers to filaments of the type described in US. Patent 2,939,201 and 2,939,202. These trilobal filaments are characterizedby tip radius ratio, modification ratio, and arm angle, all of these parameters being described in detail in the above patents. Among the trilobal filaments of US. Patent 2,939,201, the greatest problem with respect to streakiness is encountered with those which fall within ovoid QST as shown in that patent and consequently the present invention is of greatest value in this area. j w

In order to achieve the desired improvement in fabric uniformity, the filaments must vary in denier over a range such that the coefficient of variation (v) is greater than 10 and preferably greater than 12. In addition, however, the distribution of filaments within this range must be such that the skewness coefficient (a is in the range of 0.7 to +0.7 and the kurtosis coefiicient is not greater than 4.0 and preferably in the range of 1 to 4. As illustrated in the examples, the filament deniers should be distributed in a reasonably uniform fashion over the range selected. A skewed distribution, as shown for yarn D of Example I, leads to unsatisfactory results.

This invention is obviously applicable only to multi filament yarns. While the applicability of the invention will vary depending upon the type of yarn, it is generally useful for high-luster, trilobal filament yarns containing ten or more filaments.

It must be appreciated, of course, that yarns which are nominally of constant filament denier, exhibit some variation in denier among the filaments in the yarn. This is illustrated bythe control yarn in Example I, This variation is generally not sufficient to achieve the purpose of this invention, although, for short periods where control of the process may be poor, a relatively wide spread in filament denier may be encountered. Such uncontrolled variations, however, aggravate the problem of streakiness in fabrics. Surprisingly, this invention, by deliberately imposing a continuous variation in filament denier within the yarn, achieves a marked improvement in fabric uniformity. Although some uncontrolled denier variation may still occur and be superimposed on the deliberately imposed denier variation, such variations have far less effeet on fabric uniformity than in the case where an attempt is made to prepare yarn with constant filament denier. It is to be understood, therefore, that this invention is not concerned with the production of relatively short lengths of yarn which vary considerably in filament denier but rather contemplates the production of packages or a plurality of packages of high-luster yarn wherein substantially the entire length of yarn has the required filament denier variation. The yarn packages referred to may, of course, be small packages such as cones, spools, pirns, and the like, or may be beams of yarn weighing hundreds of pounds.

This application is a continuation-in-part of application Serial No. 193,870, filed May 10, 1962.

As many different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that this invention is not to be limited to the specific embodiments thereof except as defined in the appended claims.

I claim as my invention:

1. A yarn package of continuous-filament, synthetic, textile yarn, said yarn being composed of a plurality of species of trilobal filaments, the individual filaments within each species being of essentially the same denier, but the species differing from each other in said respect, the distribution of denier values over the entire group of filaments constituting the yarn being such as to give the group 1) a coefficient of variation (v) of at least 10,

(2) a skewness coefiicient (a within the range of -0.7 to +0.7, and

F (3) a kurtosis coefficient (a in the range of 1.0 to

2. A yarn package as in claim 1, the number of species being at least five.

3. A yarn package as in claim 2, wherein no species contains more than 35% of the total number of filaments in the yarn and wherein the difference in denier between any two species which are adjacent to each other in the distribution does not exceed 35 of the average denier value for all the filaments in the yarn.

4. Fabric containing yarns as defined in claim 3.

5. A yarn package as in claim 1, said trilobal filaments being polyamide filaments.

6. Fabric containing yarns as defined in claim 1.

References Cited inthe file of this patent UNITED STATES PATENTS White June 19, 1956 Holland June 7, 1960 Swerdloil et al I an. 24, 1961 Jamieson et al Apr. 18, 1961 Bottorf May 8, 1962 Gibbins Oct. 16, 1962 Kay et al June 11, 1963 McKinney July 16, 1963 FOREIGN PATENTS Canada Mar. 24, 1959 

1. A YARN PACKAGE OF CONTINUOUS-FILAMENT, SYNTHETIC, TEXTILE YARN, SAID YARN BEING COMPOSED OF A PLURALITY OF SPECIES OF TRILOBAL FILAMENTS, THE INDIVIDUAL FILAMENTS WITHIN EACH SPECIES BEING OF ESSENTIALLY THE SAME DENIER, BUT THE SPECIES DIFFERING FROM EACH OTHER IN SAID RESPECT, THE DISTRIBUTION OF DENIER VALUES OVER THE ENTIRE GROUP OF FILAMENTS CONSTITUTING THE YARN BEING SUCH AS TO GIVE THE GROUP (1) A COEFFICIENT OF VARIATION (V) OF AT LEAST 10, (2) A SKEWNESS COEFFICIENT (A3) WITHIN THE RANGE OF -0.7 TO +0.7, AND (3) A KURTOSIS COEFFICIENT (A4) IN THE RANGE OF 1.0 TO 4.0. 